I would agree with most of your reasons, but for each of them you need to ask "why" until you get to the real source of the problem.

For the most part, the greediness of people is why we had such ridiculously leveraged financial securities and special-purpose vehicles etc. designed to stuff as many fistfuls of cash as possible into the pockets of those who could game the system the best.

Greed was the cause, and insane levels of leverage were the flimsy supports for this recent collapse of the financial house of cards.

Of course, that's not to say leverage is inherently bad, but in excess it clearly points the way to financial ruin.